Where does “réasún” come from?

réasún (Irish) comes from Middle Irish résún, from Anglo-Norman raisun, from Old French reson, from Latin ratiō, from Latin -tiō, from Latin dissertātiō, from Latin dissertus, from Latin disserere — small stone, pebble; gravel, rubble.

réasún (Irish): reason, reasoning faculty; reasonableness, sense;...

Definitions

reason, reasoning faculty; reasonableness, sense;...

Ancestry of “réasún”, step by step

Step	Language	Word	Meaning
1	Middle Irish	résún	reason
2	Anglo-Norman	raisun	Alternative form of reson
3	Old French	reson	logic, logical reasoning
4	Latin	ratiō	reason, reasoning, explanation, ground, motive, rationality, rationale, purpose
5	Latin	-tiō	tion, -ation, -ing
6	Latin	dissertātiō	(spoken) dissertation, discourse, disquisition
7	Latin	dissertus	arranged, disposed; explained
8	Latin	disserere	second-person singular future passive indicative...
9	Latin	dis-	asunder, apart, in two; reversal, removal;...
10	Latin	calceus	shoe
11	Latin	calx	limestone; chalk; the finish line
12	Ancient Greek	χάλιξ	small stone, pebble; gravel, rubble

Words derived from “réasún”

Every word from Ancient Greek χάλιξ →Every word from Latin -tiō →Every word from Latin dis- →